摘要
鲂属(Magalobrama)鱼类在我国分布很广，是一类较大型的经济鱼类，以其肉味腴美而著名。鲂鱼具有三个可贵的优点：(1)主要的食物为水草；(2)可在湖泊等静止水体中产卵繁殖；(3)生长比较迅速。无论是在发展湖泊渔业方面，抑或是在扩大淡水养殖品种方面，鲂鱼将成为主要的对象之一。因而掌握它们的生态习性和活动规律，有着重大的意义。
The two species of the genus Megalobrama are delicious food-fishes. Megalobrama terrninalis is more widly distributed; whereas the distribution of M. amblycephala is limited to lakes of the middle and lower Yangtze-kiang valley. As far as I am aware, the biology of these fishes is very incompletely known. During the year 1956 to 1957, a biological study of these fishes was undertaken in Lake Liang-Tze, Hupeh Province, and the results are dealt with here. The growth, the habitat, the age determination, the fluctuation of the metric and numeral characters, the reproduction and embryonic development, etc. form the principal items of this investigation. M. amblycephala is one of the herbivorus fishes, it feeds mainly on the aquatic plants, among which Vallisneria spiralis L. appears the most important. M. terminalis feeds on both the aquatic plants and the fresh-water mytilid—Lirnnoperna lacustris (V. Martens). The age of these fishes can be determined by the intersection of the different groups of circuli on the scale and also by the difference between the dense and loose groups of circuli. The time of the annulus formation is in May and June. The body lengths representing the growth rates of both fishes are nearly the same. One year old individuals measure 120—230 mm. in body length and 2 years old individuals measure 250—320 mm. These measurements are corkelated with the calculation from the scale reading which is made from the focus to the boundary line between the lateral field and the posterior field. Individuals of one year and 2 years old formthe main component of the catch. Generally M. amblycephala of 2 years old, and M. terminalis of 3 years old ottain the sexual maturity. At the same age, a gravid M. amblycephala produces more eggs than that of M. termi- nalis. The breeding seasons of the two species are almost the same. Commencing from early May to late June, when the water temperature ranges from 19° to 28℃. During the breeding season, pearl organs appear at the caudal peduncle, suborbital and back of body, more in male than in female. The spawning ground is situated in the locality of the lake where the flowing of water is slow. The eggs adhere to the aquatic plants. The embryonic development of the M. arnblycephala observed in the aquaria shows that hatching takes place 44 hrs. after fertization at the temperature of 20°— 25℃. In the winter, schools of M. amblycephala are usually found in muddy concave areas at bottom of the lake, but those of M. terminalis hide between rocks. The impovement of the natural resources of these fishes in Liang-Tze Lake is also discussed.
